(Sen) - Scientists have proposed a new theory that the Earth and Moon were created after two planetary bodies, each five times larger than Mars, collided. The two similar sized bodies then re-collided and formed Earth surrounded by a disk of material that eventually formed the Moon, leaving the two bodies with the similar chemical compositions found today.
The new formation model was developed by Robin M. Canup of the Southwest Research Institute in San Antonio, Texas and was funded by the NASA Lunar Science Institute (NLSI). Canup said "The ultimate likelihood of each impact scenario will need to be assessed by improved models of terrestrial planet formation." Canup's model accounts for the similarity in composition of the Earth and Moon.
The generally accepted view is that the Moon was formed after a Mars sized body - which theorists have named Theia - crashed into Earth, ejecting a disc of material orbiting Earth that clumped together to form the Moon. However, Theia is likely to have had a different chemical composition to Earth, and modelling of the impact suggested that the Moon should be made up of material from the impacting world Theia. Yet our exploration of the Moon has taught us that it is made of the same material as Earth, a puzzling feature of the Theia impact theory known as the Lunar Paradox. The new collision model explains how the Earth and the Moon would have formed with similar composition, without throwing up any Lunar Paradox.
NLSI Deputy Director Greg Schmidt said: "Our understanding of the solar system is constantly being refined with each new discovery. This research illustrates the importance of modeling planetary formation to enhance our scientific understanding of the moon and its place in the solar system."
Although the new formation theory avoids the Lunar Paradox, researchers at the University of Bern, Switzerland, recently published a paper suggesting a resolution to the paradox even assuming the conventional formation theory of Theia's impact. The researchers, led by Andreas Reufer, simulated different impact speeds and trajectories, including 'hit and run' collisions which result in a substantial amount of material being lost to space. The simulations produced a much closer match to the Earth-Moon composition seen today and suggested that Theia's impact would not necessarily have created the Lunar Paradox after all.
Canup's research paper, entitled "Forming a Moon with an Earth-like composition via a Giant Impact" was recently published in the journal Science online.
The Sun was born about 4.6 billion years ago and the planets formed within a few hundred million years of the Sun's birth.